Apparatus for refining iron



Nov. 2, 1965 KURO KANAMORI APPARATUS FOR REFINING IRON Filed Nov. 13.1963 INVENTOR. KURO KANAMORI BY A torney 1 United States Patent C)3,215,424 APPARATUS FOR REFINING IRON Karo Kanamori, 36 AsagayaS-chorne, Suginami-ku, Tokyo, Japan Filed Nov. 13, 1961, Ser. No.151,918 Claims priority, application Japan, Dec. 7, 1960, 35/ 47,802 1Claim. (Cl, 266-34) The present invention relates to an apparatus forrefining iron with oxygen or an oxygen-containing gas.

The primary object of the invention is to provide an apparatus forrefining iron by continuously making slag and continuously removingslag, thereby causing active slag to contact continuously the surface ofmolten iron, while circulating said molten iron along the center line ofannular path.

Another object of the invention is to provide an apparatus for refiningiron comprising means to impart a controllable uniform circular fiow tothe molten iron, while it is being exposed simultaneously to a reactionwith a refining gas and/ or solids in the reaction chamber.

Yet another object of the invention is to impart the circular flowmentioned, to the molten metal in the reaction chamber mechanically.

Still another object of the invention is to impart the circular flow,mentioned, to the molten iron, by directing the refining gas and/orsolids for reaction toward it in a directional stream in the reactionchamber.

Another object of the invention is to provide an apparatus for refiningiron with means to adjust the velocity of fiow of the molten materialmentioned within a predetermined range of zones.

Yet another object of the invention is to provide an apparatus of thekind mentioned, permitting the use and advantageous utilization of thesolids used conventionally as slag-making and refining agents, in powderform either separated from or in mixture with the refining gasesselected.

Still another object of the invention is to provide an apparatus forrefining iron of the kind mentioned with means permitting introductionof the slag-making and refining agents.

Other objects of the invention will become clear from the followingdetailed description and accompanying drawings.

A preferred embodiment of the apparatus of this invention will now beexplained with reference to the attached drawings.

FIG. 1 is a front view partly in perspective and partly in longitudinalsection of a sample apparatus of this invention, and FIG. 2 is a crosssection taken on line 22 of FIG. 1.

and it is preferable to use materials in powder form. The gas and thesolids are used separately or as a mixture.

The refining chamber of an annular form is made by forming an annularspace with refractory materials along 3,215,424 Patented Nov. 2, 1965the circumference of a circle of the size selected depending uponspecific conditions of operation, and the longitudinal sections of anypositions of said space show the substantially same shape.

Although this annular space may be open towards the top, it is possibleto form an annular space with a closed top made of refractory materialsin a similar way, if desired or if occasions require. The refractorymaterials are generally covered by a steel shell, and an iron tappinghole, a slag running outlet, an exhaust pipe, nozzles and/ or aslag-removing stopper can be installed as desired. The molten iron ismaintained in the annular space or the refining chamber and refined bymaking a circular motion.

In FIG. 1 and FIG. 2, the numerical figures 1, 3 and 4 show the lowerpart furnace body, the lower part steel shell and the lower partrefractory materials, respectively. 5 represents the refining chamberand 6 represents the molten iron. 7, 8 and 9 show respectively, theupper part furnace body, the upper part steel shell and the upper partrefractory materials. 10, 11 and 12 represent, respectively, the steeltapping hole, the slag removing outlet and the nozzles. 13, 14 and 15represent, respectively, the exhaust pipe, the stopper for removingslags and the inlet for a molten metal. The arrow mark A shows thedirection of the circulation of flow of the molten iron and slags.

A preferable method for reacting the gas and/ or solids with the molteniron is to provide over the surface of the molten metal one or severalnozzles which are stationary or changeable in direction and position,and blow the gas and/ or solids over the surface of the molten metal orpour them into the molten metal from a direction aslant to said surfacesuch as, for example, from the angle of 45 degrees.

According to this invention, it is possible to install a larger numberof nozzles or inlets for blowing the refining gas and solids than inconventional converters and open-hearth furnaces. Therefore, not only isit possible to freely select the zones for blowing or adding materialsfor refining but also it is possible to greatly increase or decrease thequantity of materials to be blown into or to be added, with result thata very quick andrapid refining is made possible.

The position of the nozzles can be freely adjusted depending upon thekind of steel desired and on the conditions of refining. Therefore, whenthe slag is low in temperature, of high viscosity and hard to flow, theangle of the nozzles and the distance of their tips from the surface ofthe molten bath are adjustable to be switched to the so-called surfaceblow. In this way, CO in exhaust gas is burnt into CO and thetemperature within the furnace above the molten iron is rapidly elevatedwith the result that the fluidity of slag is increased, and the removalof slag can be smoothly carried out.

Molten pig iron is first introduced through the inlet 15 into thefurnace preheated by a burner. Oxygen is blown from the nozzles 12 intothe molten pig iron, and the refining starts to take place bycirculating the molten pig iron by the velocity energy of flow of theoxygen.

The advantageous effects arising from the refining according to thisinvention are hereinafter described.

The molten iron oxidized at the zone to which a refining gas such as,for example, an oxygen gas has been blown, and the produced slags moveforward by the circular motion, and fresh molten iron, which has not yetbeen oxidized, continually moves forward to said zone where it isoxidized and then further moves on, and thus the circular motion isrepeated until the refining is completed. In this way, a uniformoxidation of the molten iron is secured.

According to this invention, the temperature of the zone to which oxygenhas been blown is not locally raised due to the circulation of themolten iron and slags, and thus it is possible to carry out the refiningof iron by adjusting the temperature of the molten iron within aspecific range, always pushing a white-heat point ahead.

Slag-making agents are added either through an inlet (not shown in thedrawings) at a proper time or through the nozzles 12 together with therefining gas. The exhaust gas goes out of the exhaust pipe or stack 13.

In the course of the refining operation, slags only are caught by thestopper 14 and are removed from the outlet 11. The amount of slag whichcirculates with the molten iron and the amount of slag to be removed areincreased or decreased in volume by adjusting the height of said stopper14.

When a stopper is provided in the course of the circulation of themolten iron and slags, the molten iron will pass under the stopper andcontinue to take the circular motion, while the stopper is soconstructed as to catch only the slags floating on the molten iron. Itis thus possible to remove the produced slags continually or at anypreferred time, as occasions may require. According to this method, itis possible to avoid the disadvantage of removing slag by discontinuingthe refining operation as in the double slag-process carried out in theconventional converters, and therefore this method is very advantageousin the refining of pig iron such as, for example, one containing a highpercentage of silicon or phosphorus.

When the molten iron and slag circulate, the slag is affected by thevelocity energy of the gas which is over them and there will arise aditference in the velocity of circulation between the slag and themolten metal, with the result that the interfacial reaction of themolten iron and slag takes place very actively. It is thus possible tocombine an open-hearth furnace process with a converter process.

In case a closed refining chamber is employed, an exhaust gas passesthrough the inside of the furnace, circulating around the slag and themolten metal, and goes out of a stack. Consequently, the high heat whichthe gas possesses in the course of going through the inside of theannular furnace can be fully utilized for the refining itself. Aceordingto this invention, therefore, thermal efficiency is greatly improved incomparison to the conventional converter process in which the gas israpidly discharged from a steel bath to the outside of the furnace.

The progress of refining can be determined by taking analysis samplesand measuring the temperature of the molten metal through said outletand said inlet for adding slag-producing agents. Accordingly, theoperation can be simultaneously controlled.

At the last stage of refining a deoxidizing agent is supplied through aproper inlet (not shown in the drawings) or with the stream of gas, andthen steel is taken out of the steel tapping hole 10.

EXAMPLE I An annular furnace of 100 kg. capacity as shown in thedrawings is used. The quantity of molten pig iron is 102 kg., and afterthe introduction of the molten iron into the furnace the blowing andrefining start to take place at the temperature of 1290 C. The blowingand refining time is 11 minutes and 30 seconds in total, and pure oxygenis blown into the furnace from two nozzles. The pressure of oxygen isapproximately 4-5 kg./cm. and the quantity is 0.62 m. /min. for thefirst 5 minutes, and 0.81 m. /min. for the rest of time and refining iscarried out continuously. Towards the end of refining a part of slags isremoved while refining. Samples of slags and the molten metal are takenfrom the slag removing outlet four times during the entire refining timeas shown in Table I to determine the progress of refining.

As slag producing agents, 3.0 kg. of CaO and 0.6 kg. of CaF are suppliedimmediately after the starting of blowing and refining, and 4.0 kg. ofCaO and 0.8 kg. of CaF are supplied after the lapse of 5 minutes and 30seconds. 2.0 kg. of Fe-Mn powder is supplied as a deoxidizing agentafter the lapse of 11 minutes from the starting.

Table I At the. 5 minutes 9 minutes At the time of la r later time ofstarting t pp 4. 26 2. 75 0. 37 0. 0s 1. 01 0. 36 0.33 trace 0. 91 0.092 0.11 0. 320 0. 260 0. 068 0. 05s 0. 053 0. 014 0. 014 0. 004

As the result of this operation, 80.8 kg. of steel were obtained and thetapping temperature of steel was 1640 C.

EXAMPLE II The procedure of Example I is followed except that thequantity of oxygen is 0.60 m. min. constantly throughout the operationand the nozzles are placed a little closer to the face of the moltenmetal. The result is shown in Table II.

Table 11 At the 5 minutes 9 minutes At the time of ter later time ofstarting pp 4. 35 2. 74 0. 45 0. 10 0.85 0.31 0. 26 0. 2G 0. 92 0. 22 0.053 0.31 0. 21 0. 04 0. ()6 Trace 0. 069 0. 038 0. 014 0. 004

As the result of this operation, 87.6 kg. of steel were obtained, andthe tapping temperature of steel was 1640 C.

While refining was carried out in such a short period of time, it wasalso possible to completely avoid slopping by removing slags at propertimes.

The oxidation of silicon, manganese, carbon etc. in the molten iron isregulated by their atfinity with oxygen and the temperature. In theconventional converters, oxidation sometimes concentrically takes placeat the zone to which oxygen is blown, resulting in a difference in thedegree of oxidation from other zones. According to this invention, sincethe refining operation is carried out while circulating the molten ironand slags, the white-heat point gradually moves forward and the molteniron is uniformly refined according to the oxidation step in metallurgy.This fact is particularly advantageous in the case of the refining of,for example, chromium-containing pig iron smelted from laterite ores.

As described above, this invention achieves very superior eifects whichcannot be expected to be attained by the conventional apparatus.

The present specification describes examples of an invention for thepurposes here disclosed. It is, however, intended to cover all changesand modifications of the embodiments shown which do not depart from thespirit and scope of the invention as claimed.

I claim:

A furnace comprising a hollow torus, conduit means for introducingmolten metal into the torus and for removing m lt n metal therefrom,nozzle means extending into the hollow of the torus at an angle to thecenterline thereof for introducing refining agents therein, an outletfor removing slag formed on the surface of the molten metal, and abarrier means supported within and extending radially of the torusadjacent said slag removing outlet and positioned to bar the passage ofslag and allow the passage of molten metal past said barrier means.

References Cited by the Examiner UNITED STATES PATENTS 6 Greene 75-52 XNeuhauss 75-60 X Whiston 266-33 Geyer 75-61 X Alexandrovsky 75-60 Leroyet a1 75-52 X Rummel 75-93 FOREIGN PATENTS Great Britain.

252,046 10/12 Germany.

BENJAMIN HENKIN, Primary Examiner.

' RAY K. WINDHA'M, Examiner.

